1. Field of the Invention
the present invention relates generally to ATM (asynchronous transfer mode) switching systems, and more specifically to an ATM switching system particularly suitable for varying traffic patterns.
2. Description of the Related Art
For broadband ISDN, optical links will be used to interconnect a plurality of ATM network nodes in which the links are connected to an ATM switching module via an array of interface units where conversion is performed between optical signals and electrical signals. In the ATM system, a plurality of ATM data streams destined for different destinations can be statistically multiplexed into a single data stream, and the latter may be demultiplexed at a network node into the component streams according to the destination addresses contained in the cell headers of the component streams. However, the entry point of the node where the multiplexed signal appears is interfaced with an opto-electrical converter and the exit points where the demultiplexed components appear are interfaced with respective electro-optical converters. Thus, the numbers of O/E and E/O converters of an ATM network node may differ from each other. This is undesirable from the design standpoint of an ATM switching system because of the difficulty to predict the number of such interface units which will be required in the future. This asymmetric relationship is further compounded by the fact that, in the B-ISDN, the traffic pattern of each network node varies significantly due to the wide range of services that need different transmission speeds, or bandwidths. Particularly, the outgoing and incoming traffic volumes of a video service provider are significantly greater than the corresponding traffic volumes of its subscribers.
One approach is to employ an optical distribution frame to establish connections between the optical transmission links and the input and output ports of the ATM switching module.
However, in order to meet a wide range of varying traffic patterns the distribution frame is not satisfactory for reconfiguring the connections to such an extent that the ATM switching module operates at the best possible efficiency. In addition, manual work is involved when reconfiguring the connections.